Research On Sedimentary Characteristics Of Nantun Formation In Northern Area Of Wuerxun Depression

Based on the most newest theories and methods of Sequence Stratigraphy, Seismic Stratigraphy and Sedimentology, the sequence characteristics as well as sedimentary facies distributions in NanTun Formation in the Northern area of WuErxun Depression were analyzed and researched in detail in this paper, integrated with sufficient cores observation, and seismic, logging data analyzing. Moreover, combined with the structural geology features of that area, sedimentary characteristics researching and favorable facies belt distribution prediction were also processed. Consequently, abundantly reliable basises for sequence division could be achieved in this paper, which can definitely provide great supportions for the future exploration and development in that area.NanTun formation was classified into two third-order sequences, and seven fourth-order sequences elaborately in this paper. Some likely aspects can be illustrated:Firstly, completedly developed system domains exist in each third-order sequence. Secondly, the interface of two adjacent sequences shows evident lithology and electrical conversion. Finally, these sequence interfaces are partly truncated underside, and onlaped above.Based on seismic, logging and core data, combined with the studies of gully, slope break and synsedimentary fault, integrated with the analysis of seismic attributes, stratum and sandstone distribution, as well as heavy mineral characteristics, the conclusion that four mainly facies including braided fluvial delta facies, fan-delta facies and lacustrine facies, as well as two secondary facies compsed of volcanic facies and lake fan facies, were developed in the NanTun formation, have be arrived. Furthermore, the depositional system distributions of the fourth-order sequence, as well as the depositional patterns in the northern area of WuErxun Depression were also identified in this paper.At last, based on the comprehensively analysis of basic hydrocarbon accumulation conditions such source bed, reservoir area, cap rock and so on, as well as the sandstones distribution and other researching results, the favorable belt in this area was predicted.